1. Field of the Invention
The present invention relates to organopolysiloxane compositions which are hardenable to elastomers at ambient temperature, and, more especially, to such compositions comprising acyloxy radicals bonded to silicon atoms and further including hardening accelerators which comprise hydroxides of the alkali and alkaline earth metals.
The subject compositions, in contrast to the known one-component compositions also comprising acyloxy radicals bonded to silicon atoms (described, in particular, in French Pat. Nos. 1,198,749, 1,220,348 and 2,429,811, U.S. Pat. No. 3,133,891, and published French Application No. 82/13,505, filed on July 30, 1982), are not stable upon storage, but the time required for the cross-linking thereof is much shorter, for example, on the order of a few minutes up to 60 minutes. They must therefore be directly prepared as and when required.
The subject compositions are also capable of being employed in fields of application which require a short cross-linking time regardless of the degree of humidity of the surrounding atmosphere, such as the production of an "in situ" seal in the automobile industry.
2. Description of the Prior Art
Organopolysiloxane compositions comprising acyloxy radicals bonded to silicon atoms, whose cross-linking time is independent of the humidity of the ambient air are known to this art; compare, for example, British Patent Specification No. 1,308,985. More precisely, this patent relates to a process of hardening consisting of adding to the above compositions from 3 to 15% of a sodium silico-aluminate having from 5 to 15% by weight of adsorbed water.
This prior art process makes it possible to manufacture silicone elastomer molded shaped articles by low pressure injection. However, British Patent Specification No. 1,308,985 teaches that it is necessary to attain relatively short hardening times, for example, on the order of 30 minutes, to introduce large amounts of sodium silico-aluminate (15% in the table on page 2); this has the disadvantage of impairing the mechanical properties of the elastomers produced from the compositions. Furthermore, the patent does not mention the means required to obtain cross-linking times less than 30 minutes. Cf. British Patent Specification Nos. 640,067 and 1,181,346.
Consequently, serious need exists in this art for organopolysiloxane compositions comprising acyloxy radicals bonded to silicon atoms, rapidly hardening at ambient temperature, regardless of air humidity, and still providing elastomers having good mechanical properties.
This combination of properties would make it possible, among other things, to employ such compositions for the gluing or sealing of components;
(1) moving on industrial assembly lines, or
(2) for which no storage areas are available to ensure their complete hardening.